<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
 <head>
  <meta http-equiv="content-type" content="text/html; charset=UTF-8">
  <title>Acquire a semaphore</title>
 </head>
 <body class="docs"><div id="layout">
  <div id="layout-content"><div id="function.sem-acquire" class="refentry">
 <div class="refnamediv">
  <h1 class="refname">sem_acquire</h1>
  <p class="verinfo">(PHP 4, PHP 5, PHP 7)</p><p class="refpurpose"><span class="refname">sem_acquire</span> &mdash; <span class="dc-title">Acquire a semaphore</span></p>

 </div>
 
 <div class="refsect1 description" id="refsect1-function.sem-acquire-description">
  <h3 class="title">说明</h3>
  <div class="methodsynopsis dc-description">
   <span class="methodname"><strong>sem_acquire</strong></span>
    ( <span class="methodparam"><span class="type">resource</span> <code class="parameter">$sem_identifier</code></span>
   [, <span class="methodparam"><span class="type">bool</span> <code class="parameter">$nowait</code><span class="initializer"> = <strong><code>FALSE</code></strong></span></span>
  ] ) : <span class="type">bool</span></div>

  <p class="para rdfs-comment">
   <span class="function"><strong>sem_acquire()</strong></span> by default blocks (if necessary) until the
   semaphore can be acquired.  A process attempting to acquire a semaphore which
   it has already acquired will block forever if acquiring the semaphore would
   cause its maximum number of semaphore to be exceeded.
  </p>
  <p class="para">
   After processing a request, any semaphores acquired by the process but not
   explicitly released will be released automatically and a warning will be
   generated.
  </p>
 </div>

 
 <div class="refsect1 parameters" id="refsect1-function.sem-acquire-parameters">
  <h3 class="title">参数</h3>
  <p class="para">
   <dl>

    
     <dt>
<code class="parameter">sem_identifier</code></dt>

     <dd>

      <p class="para">
       <code class="parameter">sem_identifier</code> is a semaphore resource,
       obtained from <span class="function"><a href="sem_get.html" class="function">sem_get()</a></span>.
      </p>
     </dd>

    
    
     <dt>
<code class="parameter">nowait</code></dt>

     <dd>

      <p class="para">
       Specifies if the process shouldn&#039;t wait for the semaphore to be acquired.
       If set to <em>true</em>, the call will return
       <em>false</em> immediately if a semaphore cannot be immediately
       acquired.
      </p>
     </dd>

    
   </dl>

  </p>
 </div>

 
 <div class="refsect1 returnvalues" id="refsect1-function.sem-acquire-returnvalues">
  <h3 class="title">返回值</h3>
  <p class="para">
   成功时返回 <strong><code>TRUE</code></strong>， 或者在失败时返回 <strong><code>FALSE</code></strong>。
  </p>
 </div>

 
 <div class="refsect1 changelog" id="refsect1-function.sem-acquire-changelog">
  <h3 class="title">更新日志</h3>
  <p class="para">
   <table class="doctable informaltable">
    
     <thead>
      <tr>
       <th>版本</th>
       <th>说明</th>
      </tr>

     </thead>

     <tbody class="tbody">
      <tr>
       <td>5.6.1</td>
       <td>
        The <code class="parameter">$nowait</code> parameter was added.
       </td>
      </tr>

     </tbody>
    
   </table>

  </p>
 </div>

 
 <div class="refsect1 seealso" id="refsect1-function.sem-acquire-seealso">
  <h3 class="title">参见</h3>
  <p class="para">
   <ul class="simplelist">
    <li class="member"><span class="function"><a href="sem_get.html" class="function" rel="rdfs-seeAlso">sem_get()</a> - Get a semaphore id</span></li>
    <li class="member"><span class="function"><a href="sem_release.html" class="function" rel="rdfs-seeAlso">sem_release()</a> - Release a semaphore</span></li>
   </ul>
  </p>
 </div>
  
 
</div></div></div></body></html>